Standing in REAL ; Failing in model

Hi All,

i have modelled a wall mounted bracket supporting a 300 x 90 Dc PFC column. members 53 is failing in Compression for load of 46.10 but member 52 is passing in 49.58 Comprexssion. Both member are part of single beam only. Same is happening with 54 & 55.

This doesnt make any sense.

I have atached the STAAD file as well as drawing for this bracket.

 

Please help me solve this.

 

Thanks in advance

47073914-SW-CV-CALC-MOD-102-R4.std

Parents
  • It might help to view the Track 2 output for the two members side by side. I've attached them here. What I notice is some differences in the effective length and Mx demand that probably account for the difference in the final utilization ratio.

     ALL UNITS ARE - KN   METE (UNLESS OTHERWISE Noted)
     
     MEMBER     TABLE       RESULT/   CRITICAL COND/     RATIO/     LOADING/
                              FX            MY             MZ       LOCATION
     =======================================================================
     
    
          52 ST UA150X150X18  PASS     BS-4.8.3.3.1       0.968         9
                            49.58 C          0.46          17.00        -
     =======================================================================
       MATERIAL DATA
          Grade of steel           =  S 275
          Modulus of elasticity    =  205 kN/mm2
          Design Strength  (py)    =  265  N/mm2
     
       SECTION PROPERTIES (units - cm)
          Member Length =     37.20
          Gross Area =   51.00  Net Area =   51.00  Eff. Area =   51.00
     
                                        z-z  axis       y-y  axis
          Moment of inertia        :      434.846        1691.576
          Plastic modulus          :      126.078         287.070
          Elastic modulus          :       70.044         159.483
          Effective modulus        :       70.044         159.483
          Shear Area               :       16.200          16.200
     
       DESIGN DATA (units - kN,m)   BS5950-1/2000
          Section Class            :   SEMI-COMPACT
          Squash Load              :   1351.50
          Axial force/Squash load  :     0.037
     
                                        z-z  axis       y-y  axis
          Compression Capacity     :       1301.8         1208.5
          Tension Capacity         :       1351.5         1351.5
          Moment Capacity          :         18.6           42.3
          Reduced Moment Capacity  :         18.6           42.3
          Shear Capacity           :        257.6          257.6
     
       BUCKLING CALCULATIONS (units - kN,m)
       (axis nomenclature as per design code)
                                     v-v axis      a-a axis       b-b axis
          Slenderness              :   23.918        35.761         35.761
          Radius of gyration (cm)  :    2.920         4.520          4.520
          Effective Length         :    0.372         0.372          0.372
        STAAD SPACE                                              -- PAGE NO.   46
    
     
          LTB Moment Capacity (kNm) and LTB Length (m):    42.26,    0.372
          LTB Coefficients & Associated Moments (kNm):
          mLT =   1.00  :   mx =   1.00   :  my =   1.00   :  myx =   0.00
          Mlt =    0.46 :   Mx =   17.00  :  My =   0.46   :   My =   0.00
     
       CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m):
     
        CLAUSE        RATIO  LOAD     FX       VY      VZ      MZ      MY
       BS-4.2.3-(Y)   0.191     9      -      49.2      -       -       -
       BS-4.2.3-(Z)   0.018     8      -        -      4.5      -       -
       BS-4.3.6       0.039     8      -      38.0      -       -      1.7
       BS-4.7   (C)   0.041     9    49.6       -       -       -       -
       BS-4.8.2.2     0.017     1     1.1      1.0     0.1     0.3     0.0
       BS-4.8.2.3     0.016     1     1.1       -       -      0.3     0.0
       BS-4.8.3.2     0.961     9    49.6     49.2     2.1    17.0     0.3
       BS-4.8.3.3.1   0.968     9    49.6       -       -     17.0     0.5
       BS-4.9         0.016     1     0.0       -       -      0.3     0.0
        Torsion and deflections have not been considered in the design.
     
    

     ALL UNITS ARE - KN   METE (UNLESS OTHERWISE Noted)
     
     MEMBER     TABLE       RESULT/   CRITICAL COND/     RATIO/     LOADING/
                              FX            MY             MZ       LOCATION
     =======================================================================
     
    
     *    53 ST UA150X150X18  FAIL     BS-4.8.3.3.1       1.215         8
                            46.10 C          0.09          21.80        -
     =======================================================================
       MATERIAL DATA
          Grade of steel           =  S 275
          Modulus of elasticity    =  205 kN/mm2
          Design Strength  (py)    =  265  N/mm2
     
       SECTION PROPERTIES (units - cm)
          Member Length =     48.60
          Gross Area =   51.00  Net Area =   51.00  Eff. Area =   51.00
     
                                        z-z  axis       y-y  axis
          Moment of inertia        :      434.846        1691.576
          Plastic modulus          :      126.078         287.070
          Elastic modulus          :       70.044         159.483
          Effective modulus        :       70.044         159.483
          Shear Area               :       16.200          16.200
     
       DESIGN DATA (units - kN,m)   BS5950-1/2000
          Section Class            :   SEMI-COMPACT
          Squash Load              :   1351.50
          Axial force/Squash load  :     0.034
     
                                        z-z  axis       y-y  axis
          Compression Capacity     :       1280.6         1194.2
          Tension Capacity         :       1351.5         1351.5
          Moment Capacity          :         18.6           42.3
          Reduced Moment Capacity  :         18.6           42.3
          Shear Capacity           :        257.6          257.6
     
       BUCKLING CALCULATIONS (units - kN,m)
       (axis nomenclature as per design code)
                                     v-v axis      a-a axis       b-b axis
          Slenderness              :   26.651        37.527         37.527
          Radius of gyration (cm)  :    2.920         4.520          4.520
          Effective Length         :    0.486         0.486          0.486
        STAAD SPACE                                              -- PAGE NO.   48
    
     
          LTB Moment Capacity (kNm) and LTB Length (m):    42.26,    0.486
          LTB Coefficients & Associated Moments (kNm):
          mLT =   1.00  :   mx =   1.00   :  my =   1.00   :  myx =   0.00
          Mlt =    0.09 :   Mx =   21.80  :  My =   0.09   :   My =   0.00
     
       CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m):
     
        CLAUSE        RATIO  LOAD     FX       VY      VZ      MZ      MY
       BS-4.2.3-(Y)   0.180     8      -      46.4      -       -       -
       BS-4.2.3-(Z)   0.017     7      -        -      4.3      -       -
       BS-4.3.6       0.050     7      -      39.6      -       -      2.1
       BS-4.7   (C)   0.039     8    46.1       -       -       -       -
       BS-4.8.2.2     0.083     1     1.1      4.3     0.0     1.5     0.0
       BS-4.8.2.3     0.082     1     1.1       -       -      1.5     0.0
       BS-4.8.3.2     1.211     8    46.1     46.2     0.2    21.8     0.1
       BS-4.8.3.3.1   1.215     8    46.1       -       -     21.8     0.1
       BS-4.9         0.082     1     0.0       -       -      1.5     0.0
        Torsion and deflections have not been considered in the design.
    



    Answer Verified By: Mahesh Gopal 

Reply
  • It might help to view the Track 2 output for the two members side by side. I've attached them here. What I notice is some differences in the effective length and Mx demand that probably account for the difference in the final utilization ratio.

     ALL UNITS ARE - KN   METE (UNLESS OTHERWISE Noted)
     
     MEMBER     TABLE       RESULT/   CRITICAL COND/     RATIO/     LOADING/
                              FX            MY             MZ       LOCATION
     =======================================================================
     
    
          52 ST UA150X150X18  PASS     BS-4.8.3.3.1       0.968         9
                            49.58 C          0.46          17.00        -
     =======================================================================
       MATERIAL DATA
          Grade of steel           =  S 275
          Modulus of elasticity    =  205 kN/mm2
          Design Strength  (py)    =  265  N/mm2
     
       SECTION PROPERTIES (units - cm)
          Member Length =     37.20
          Gross Area =   51.00  Net Area =   51.00  Eff. Area =   51.00
     
                                        z-z  axis       y-y  axis
          Moment of inertia        :      434.846        1691.576
          Plastic modulus          :      126.078         287.070
          Elastic modulus          :       70.044         159.483
          Effective modulus        :       70.044         159.483
          Shear Area               :       16.200          16.200
     
       DESIGN DATA (units - kN,m)   BS5950-1/2000
          Section Class            :   SEMI-COMPACT
          Squash Load              :   1351.50
          Axial force/Squash load  :     0.037
     
                                        z-z  axis       y-y  axis
          Compression Capacity     :       1301.8         1208.5
          Tension Capacity         :       1351.5         1351.5
          Moment Capacity          :         18.6           42.3
          Reduced Moment Capacity  :         18.6           42.3
          Shear Capacity           :        257.6          257.6
     
       BUCKLING CALCULATIONS (units - kN,m)
       (axis nomenclature as per design code)
                                     v-v axis      a-a axis       b-b axis
          Slenderness              :   23.918        35.761         35.761
          Radius of gyration (cm)  :    2.920         4.520          4.520
          Effective Length         :    0.372         0.372          0.372
        STAAD SPACE                                              -- PAGE NO.   46
    
     
          LTB Moment Capacity (kNm) and LTB Length (m):    42.26,    0.372
          LTB Coefficients & Associated Moments (kNm):
          mLT =   1.00  :   mx =   1.00   :  my =   1.00   :  myx =   0.00
          Mlt =    0.46 :   Mx =   17.00  :  My =   0.46   :   My =   0.00
     
       CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m):
     
        CLAUSE        RATIO  LOAD     FX       VY      VZ      MZ      MY
       BS-4.2.3-(Y)   0.191     9      -      49.2      -       -       -
       BS-4.2.3-(Z)   0.018     8      -        -      4.5      -       -
       BS-4.3.6       0.039     8      -      38.0      -       -      1.7
       BS-4.7   (C)   0.041     9    49.6       -       -       -       -
       BS-4.8.2.2     0.017     1     1.1      1.0     0.1     0.3     0.0
       BS-4.8.2.3     0.016     1     1.1       -       -      0.3     0.0
       BS-4.8.3.2     0.961     9    49.6     49.2     2.1    17.0     0.3
       BS-4.8.3.3.1   0.968     9    49.6       -       -     17.0     0.5
       BS-4.9         0.016     1     0.0       -       -      0.3     0.0
        Torsion and deflections have not been considered in the design.
     
    

     ALL UNITS ARE - KN   METE (UNLESS OTHERWISE Noted)
     
     MEMBER     TABLE       RESULT/   CRITICAL COND/     RATIO/     LOADING/
                              FX            MY             MZ       LOCATION
     =======================================================================
     
    
     *    53 ST UA150X150X18  FAIL     BS-4.8.3.3.1       1.215         8
                            46.10 C          0.09          21.80        -
     =======================================================================
       MATERIAL DATA
          Grade of steel           =  S 275
          Modulus of elasticity    =  205 kN/mm2
          Design Strength  (py)    =  265  N/mm2
     
       SECTION PROPERTIES (units - cm)
          Member Length =     48.60
          Gross Area =   51.00  Net Area =   51.00  Eff. Area =   51.00
     
                                        z-z  axis       y-y  axis
          Moment of inertia        :      434.846        1691.576
          Plastic modulus          :      126.078         287.070
          Elastic modulus          :       70.044         159.483
          Effective modulus        :       70.044         159.483
          Shear Area               :       16.200          16.200
     
       DESIGN DATA (units - kN,m)   BS5950-1/2000
          Section Class            :   SEMI-COMPACT
          Squash Load              :   1351.50
          Axial force/Squash load  :     0.034
     
                                        z-z  axis       y-y  axis
          Compression Capacity     :       1280.6         1194.2
          Tension Capacity         :       1351.5         1351.5
          Moment Capacity          :         18.6           42.3
          Reduced Moment Capacity  :         18.6           42.3
          Shear Capacity           :        257.6          257.6
     
       BUCKLING CALCULATIONS (units - kN,m)
       (axis nomenclature as per design code)
                                     v-v axis      a-a axis       b-b axis
          Slenderness              :   26.651        37.527         37.527
          Radius of gyration (cm)  :    2.920         4.520          4.520
          Effective Length         :    0.486         0.486          0.486
        STAAD SPACE                                              -- PAGE NO.   48
    
     
          LTB Moment Capacity (kNm) and LTB Length (m):    42.26,    0.486
          LTB Coefficients & Associated Moments (kNm):
          mLT =   1.00  :   mx =   1.00   :  my =   1.00   :  myx =   0.00
          Mlt =    0.09 :   Mx =   21.80  :  My =   0.09   :   My =   0.00
     
       CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m):
     
        CLAUSE        RATIO  LOAD     FX       VY      VZ      MZ      MY
       BS-4.2.3-(Y)   0.180     8      -      46.4      -       -       -
       BS-4.2.3-(Z)   0.017     7      -        -      4.3      -       -
       BS-4.3.6       0.050     7      -      39.6      -       -      2.1
       BS-4.7   (C)   0.039     8    46.1       -       -       -       -
       BS-4.8.2.2     0.083     1     1.1      4.3     0.0     1.5     0.0
       BS-4.8.2.3     0.082     1     1.1       -       -      1.5     0.0
       BS-4.8.3.2     1.211     8    46.1     46.2     0.2    21.8     0.1
       BS-4.8.3.3.1   1.215     8    46.1       -       -     21.8     0.1
       BS-4.9         0.082     1     0.0       -       -      1.5     0.0
        Torsion and deflections have not been considered in the design.
    



    Answer Verified By: Mahesh Gopal 

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